1. Field of the Invention
The present invention relates to a global optimization algorithm for upscaling images that have a few distinct colors to improve the quality of such images. The invention is particularly useful for improving the quality of dark (e.g., black) text/graphics on a light (e.g., white) background, especially small-font/thin text or thin-lined graphics. The algorithm of the present invention may be embodied in a method, an apparatus such as a computer, or as a program of instructions (e.g., software) carried on a machine-readable medium.
2. Description of the Related Art
Scaling an image involves generating a new image that is larger or smaller than the original. Scaling has many applications in scanners, printers, and photo-finishing systems, and digital cameras. In the case of upscaling, the new image is larger; that is, the new image has more pixels in the horizontal and/or vertical directions than the original image. Thus, in upscaling new pixels must created.
Some conventional image upscaling methods include a smoothing operation in conjunction therewith. However, such methods do not, for example, jointly optimize estimating pixel color, classifying it into one of a plurality of regions, and estimating region boundaries subject to region continuity and edge-configuration constraints. As the inventor herein has discovered, the joint solution of constraints at multiple levels of image abstraction leads to improved image reconstruction quality.